Human evolution owes much to the common ancestral primate.
By studying primates we get a lot of clues about our evolutionary past.
http://eskeletons.org/ is a great website for showing what skeletal features these primates have in common.
Use wikipedia to create a class power point resource showing the similarities and significant differences between the major primate groups.
Introductory Task.
Each group is allocated a range of primates as below. prepare your research as a set of slides.
find a photograph of the species you have been allocated
identify whether the species is a prosimian,new world monkey,old world monkey or great ape.
identify three physical features these four groups of primates have in common.
identify the continents each group live on.
identify the significant differences between the types of primates
Group 1 research Tarsier, Marmoset, Colobus, Bonobo chimpanzees
Group 2 research Lemurs, Squirrel monkeys, Baboons, Gorillas
Group 3 research Loris, Capuchins, Macaques, Orang utans
Group 4 research Lemurs, Howlers, Proboscis Monkeys,Gibbons.
Hand your group slides into 13 Bio in Learning Resources so we can compile a class set.
What do these animals look like?
Prosimian species (tails for balance, scent important)
New World Monkeys (always arboreal,some prehensile tails, outward facing nostrils)
Old World Monkeys (terrestrial or arboreal, never prehensile tails, downward facing nostrils)
What do all Primates have in common?
Physical Characteristics
Behavioural Characteristics
Physiological Characteristics
Grasping hands
Forward facing eyes
Finger tips (not claws)
Social groups
vocal communication
suffer from the same contagious diseases
most have ability to see in colour vision
estrus cycle
What do only Humans have, that other Primates don't?
Bipedal locomotion
Larger brain capacity compared to body size than other primates.
Reduced canine teeth.
Ability to communicate by writing.
Physiologically there is not much difference between humans and apes. Human women have menopause, because they live longer than chimpanzee females. Female chimps,orangutans, gorillas and humans all have overt menstrual flow. (Other primates reabsorb the lining of the womb, called covert menstruation, wouldn't that have been a great trait to keep, wonder what the advantage of overt menstrual flow is,otherwise why did we keep that adaptation?).
For the next two questions,send me an email about what you think the answer is.
Why do you think all primates have these characteristics?
Grasping hands
Forward facing eyes
Fingertips
Social groups
Vocal communication
What do you think the humans gain from their own specialisations?
Bipedalism
Large brain capacity
Writing
Primate Family tree
What branched out when? Who are the closest relatives to each other?
Interpret the two different graphs.The information on them is based on evidence at the time. As evidence changes the graphs change. Are the times for branching similar, are the relationships constant? As new information is added the accepted dates have changed, and sometimes evidence changes the relationships as well. Tarsiers for example are now considered less like the primate ancestor than the theory once stated.
Look at the family groups along the top/side. Check out the timelines along the side/top.
What is the mya to when the common ancestor first branches off to a new group? What is the first group thought to have branched off? What is the second and the next and the next? Describe how closely related the different groups are. Do the graphs show similar relationships between all the groups? Why do the two graphs have different dates?
http://www.quia.com/jg/493058.html for a vocabulary builder on Primates, use this after the topic,not before. There are a lot of new words that this activity can reinforce for you in a fun way.
Hominin Ancestors
Biological Evolution The three main features of human biological evolution that we study are 1 changes in the skeleton 2 changes in the skull and cranium. 3 changes in the hand.
http://www.slideshare.net/Shanura/anthropology-human-evolution This slide show gives a great visual picture of the family. Don't be too shocked. These are all projections based on fossil finds and predictions.
Like the primate tree,the hominin tree has many branches, not a direct line of descent to be studied neatly.
Ardipithecus ramidus is the latest link, a hominin that lived in trees but started to use bipedal features to succeed, despite living in a forest habitat. The favoured theory that bipedalism developed in a savannah habitat has to be adjusted now. We used to have six nice tidy reasons for people becoming bipedal when they started to live in a dry savannah. Can you recall what they are? They are at the bottom of the Biological evolution section if you can't remember them now.
Unfortunately now we have to start again with our selection pressures, as the evidence suggests that ancestors were fully bipedal before they left the forest. New selection pressures have to be discussed that could give an advantage to being bipedal in a forest habitat. What would make Ardipithecus families become bipedal? What advantage would it give them? Remember survival is all about getting the best mates, food or space to live,so the argument could go that males who carried more food back to the family with their free hands were better providers, so they were more likely to get to stay around the family.
Practical task comparing the skull and cranium of hominins.
Use the skull set to measure the significant differences in the skulls we have available in class (Homo sapiens, Homo erectus, Australopithecus africanus and Gorilla). Compare the size of the forehead, brow ridges, chin, sagittal crest, zygomatic arch, mandible, angle or prognathism, the dental arcade, the position of the foramen magnum in each species.
What can you say about the trends for each feature?
Relate the biological change to a particular selection pressure that initiated the change.
Human hand evolution
link to quick animation
showing hominin hands evolving. Remember that the modern apes have also continued to evolve their hands ,and our hand is more similar to the primitive hand than they are.
The modern human hand has a longer thumb than either the chimpanzee or gorilla, relative to the overall size of the hand. This allows human hands to make the precision grip that is associated with tool use. making our opposable thumb into a precise grasp requires a longer thumb, versatile muscles and co-ordination between the hand and eyes. The area of the brain dedicated to using the hand is really large (now - probably wasn't back in the day).
It is interesting to remember that the modern human hand has more similarities to Ardipithecus style hands than it does to Gorilla or Chimpanzee as their hands have become specialised for purposes other than grasping or tool use. The chimpanzee knuckle walking style is more advanced ( which means it has changed more ) than the human or the ardipithecus hand.
What was it about human evolution that changed the selection pressures acting on our hand, what were the reasons the hand did evolve?
Hard to imagine that just being bipedal meant our hand changed - what has that go to do with walking?
Its got everything to do with NOT walking quadrupedally. Hominin hands were NOW able to be used for other lifestyle advantages. They became adapted for other things, hands could carry food so your food supply was more successful, hands could carry the children (because we were less hairy in the open savannah the dependent young couldn't cling on so well anymore) and hands could be used to start tool cultures.
Natural selection is about the selection FOR an advantage (better at competing for food, for mates or for space to live and so the offspring represent more in the next generation) so these changes to the hand are a response to these advantages being able to sue your hands more gave hominins.
This podcast describes how our anatomy allowed our hands to be more useful. http://www.npr.org/templates/story/story.php?storyId=128676181
The ongoing changes after these adaptations, and the subsequent changes in the brain , compounding with better dexterity as we used tools more and then the brain grows more and then the food is better so the brain grows more, is this never ending cycle of biology and culture interacting. (Not withstanding there has had to be some random mutation that worked out better - mutations are not a designed to order effect even if we make it sound like they are. There will have been many designs that didn't give an advantage so we don't know about them.)
Randomly Bipedalism means we have problems with our feet now!! Putting all the weight on our feet is not all good.
These guys have thought about it http://ngm.nationalgeographic.com/print/2006/07/bipedal-body/ackerman-text and how some of the health issues people have are caused by poor design. Probably doesn't affect our evolution because most of the problems arise after people have reproduced, the problems don't affect our reproductive success.
Reasons to become Bipedal in the savannah
1 Eyes were lifted up to see across a bigger distance of grassland
2 and 3 Hands were free to Carry food and weapons
4 less body area exposed to heat of sun (just the head and shoulders)
5 walking upright was more efficient over longer distances (not faster over short distances)
6 cant remember, must be another one?
Link to efossils Summary of Bipedal ism
These pages are a summary of Changes to the Skeleton to do with being Bipedal, should be all familiar stuff.
Changes in the Skull
These are caused by different selection pressures - changes in diet and changes in intelligence both affect the skull. The dietary changes is related to tool use, the trend to increasing intelligence is related to diet and to communication and problem solving, and both affect the size of the brain related to the hand.
A brief expose` of the difference in the cultures in the last 10 000 years of our history,the paleolithic, mesolithic and neolithic tool cultures. https://www.youtube.com/watch?v=-qq_1lcMrDM
This interactive In and Beyond Africa is a timeline that has information linked to the eras of human evolution, has a couple of cute games, not really year 13 level but makes a nice change from exam study eh.
Homo sapiens spread over the world.
There are several theories about how it came to pass that Homo sapiens is the only branch of hominins left on Earth. Evidence shows that Homo erectus spread out of Africa to Europe and Asia.
Did Homo erectus populations across the world continue to interbreed back wards and forwards to the populations in Africa, therefore spreading the new genes around the world and all H erectus evolved into H sapiens, OR did a successful new Homo sapiens evolve from a group in Africa, develop a successful culture and expand their population so quickly that their species did not interbreed with the previous populations, out competed the old style of living and became the only population as they migrated across the planet?
You must understand the evidence for both theories.
These are the two theories for our discussion. The Multi Regional Theory and the Replacement Theory. There is evidence for and against each theory being the correct explanation for how Homo sapiens was left as the only human species. Both theories agree that Homo erectus left Africa first.
Then they differ.
Think about what the two ideas are saying.
If the multi regional theory is supported some places will have older style fossils which will interbreed with new types and will create instantly across between the two, a half breed or transitional fossil, maybe a slopey face with a biggish forehead!! Maybe a early type fossil with tools that are more H sapiens style, these groups would make a genetic change that works for them, breed with neighbouring groups, sharing their genes around the world over a few generations. The genes they are sharing would be very diverse as they would have accumulated variations from across the world. A new cultural tool or mutation would have arisen in a variety of places, being shared widely so there would be no one specific place where oldest H sapiens tools come from. The variation in the genes would be very wide because the populations are very old.
The time span involved here is 1 million years. Generations of gene flow between many populations around the world caused the H erectus to evolve into H sapiens.
If the replacement theory is supported then the oldest sites of H sapiens fossil evidence will start off in Africa and spread out from there. The populations that left Africa probably would not interbreed back to the old groups in Africa, African populations in Africa would continue to change so their mutations would not be present in the populations that have descended from the ones that had left. The two bloodlines will be quite different. The younger descendants would have only their original DNA. like a population bottleneck, to work with. Scientists can't track the changes in nuclear DNA because of the cross over and recombination, but they can follow the mitochondrial DNA. This DNA is directly inherited from the mothers egg, only, so it is an exact copy of the mothers DNA. Any mutations between mother and child are entirely traceable. They show the family lineage as mutations accumulate. Populations that are separated will not have the same mutations that appear in the DNA.
The time span involved here is 140 000 years. This is a very recent separation. The mt DNA will not be very diverse as the population is a very small one.
What does this evidence look like?
Question 2013 NCEA
Analysis of genetic and fossil evidence (made over a number of years by a number of researchers) has indicated the following information about human dispersal:
1 Non-African males share a common ancestor about 140 000 years ago.
2 All humans share a common ancestor about 200 000 years ago.
3 Fossils (such as “Peking man” dated as about 750 000 years ago in Asia) seem to show a combination of H.sapiens and H.erectus type features.
4 Africans are more genetically diverse than other races.
5 Non-Africans include small (1-4%) traces of ancient hominin DNA (such as H neanderthalensis).
Use some or all of the above evidence to discuss the likely origin of modern humans.
In your answer:
Describe the competing theories: Multi regional and Out of Africa (also known as Replacement/Eve/recent African Origin).
Explain how the above evidence supports each theory
Justify the most likely model of human dispersal.
Best answer.....
use the dates to match the theories,
use the diversity of the DNA to match the theories,
Use all the evidence to back one theory or the other. Neither of us have to decide which one is the right one, luckily, all we have to do is analyse the evidence both sides present.
So look further into the fine points. http://www.bradshawfoundation.com/journey/ map showing timeline for Human dispersal according to one theory.
with a lot of information about the mt DNA and the Y chromosome evidence.
Variations in mt DNA are used for evidence for many human mysteries, for example the old chestnut The Russian Tsar and his family who were massacred in WWI, this interactive explains how similarities in mt DNA bases link family members. http://www.geneticorigins.org/mito/mitoframeset.htm
It is hard to understand the significance of the mt DNA, browse all the links at this page, http://humanorigins.si.edu/evidence/genetics
Study the neanderthal DNA sequences, the video, decide whether the evidence here supports the Multi-regional Theory or the Replacement Theory of Homo sapiens dispersal.
The slide show above gives evidence for each of the theories of dispersal. You might have to copy and paste the link.
And then the Neanderthal DNA found in Non Africans messes up the nice tidy theories. Remember that is why Science is always changing - as new evidence comes along, the scientists has to rethink. Can't deny the evidence. Has to alter the theory.
This clip is quite slow moving, you should know enough to understand it. https://www.youtube.com/watch?v=No_Id8H4dv8
Following the differences in neanderthal mt DNA and mutations in modern mt DNA gives a timeline for the two groups to have a common ancestor. http://www.geneticorigins.org/mito/mitoframeset.htm. You can guess your way through this interactive, but working it out is easy too.
Different angle on Dispersal.
Sometimes the question is not comparing the two theories. It is about why the population was successful and able to expand.
Why did humans leave Africa? (What were the selection pressures?) same as always - population pressure - the population got bigger where they were living) so they were under pressure to expand their range, and the environment changed ( the sea level dropped so the land bridges and islands were accessible). The population increased through better food supply, and some believe the impact of surviving grandmothers! They lived until their mid 30's now and could help their daughters raise their children, the mother had someone to give advice and get extra food for their grandchildren.
Primates
Human evolution owes much to the common ancestral primate.By studying primates we get a lot of clues about our evolutionary past.
http://eskeletons.org/ is a great website for showing what skeletal features these primates have in common.
Use wikipedia to create a class power point resource showing the similarities and significant differences between the major primate groups.
Introductory Task.
Each group is allocated a range of primates as below. prepare your research as a set of slides.
Group 1 research Tarsier, Marmoset, Colobus, Bonobo chimpanzees
Group 2 research Lemurs, Squirrel monkeys, Baboons, Gorillas
Group 3 research Loris, Capuchins, Macaques, Orang utans
Group 4 research Lemurs, Howlers, Proboscis Monkeys,Gibbons.
Hand your group slides into 13 Bio in Learning Resources so we can compile a class set.
What do these animals look like?
Prosimian species (tails for balance, scent important)
New World Monkeys (always arboreal,some prehensile tails, outward facing nostrils)
Old World Monkeys (terrestrial or arboreal, never prehensile tails, downward facing nostrils)
What do all Primates have in common?Physical Characteristics
Behavioural Characteristics
Physiological Characteristics
Grasping hands
Forward facing eyes
Finger tips (not claws)
Social groups
vocal communication
suffer from the same contagious diseases
most have ability to see in colour vision
estrus cycle
What do only Humans have, that other Primates don't?
Bipedal locomotion
Larger brain capacity compared to body size than other primates.
Reduced canine teeth.
Ability to communicate by writing.
Physiologically there is not much difference between humans and apes. Human women have menopause, because they live longer than chimpanzee females. Female chimps,orangutans, gorillas and humans all have overt menstrual flow. (Other primates reabsorb the lining of the womb, called covert menstruation, wouldn't that have been a great trait to keep, wonder what the advantage of overt menstrual flow is,otherwise why did we keep that adaptation?).
For the next two questions,send me an email about what you think the answer is.
Why do you think all primates have these characteristics?
Grasping handsForward facing eyes
Fingertips
Social groups
Vocal communication
What do you think the humans gain from their own specialisations?
BipedalismLarge brain capacity
Writing
Primate Family tree
What branched out when? Who are the closest relatives to each other?
Interpret the two different graphs.The information on them is based on evidence at the time. As evidence changes the graphs change. Are the times for branching similar, are the relationships constant? As new information is added the accepted dates have changed, and sometimes evidence changes the relationships as well. Tarsiers for example are now considered less like the primate ancestor than the theory once stated.
Look at the family groups along the top/side.
Check out the timelines along the side/top.
What is the mya to when the common ancestor first branches off to a new group?
What is the first group thought to have branched off?
What is the second and the next and the next?
Describe how closely related the different groups are. Do the graphs show similar relationships between all the groups?
Why do the two graphs have different dates?
http://www.quia.com/jg/493058.html for a vocabulary builder on Primates, use this after the topic,not before. There are a lot of new words that this activity can reinforce for you in a fun way.
Hominin Ancestors
Biological Evolution
The three main features of human biological evolution that we study are
1 changes in the skeleton
2 changes in the skull and cranium.
3 changes in the hand.
http://www.slideshare.net/Shanura/anthropology-human-evolution This slide show gives a great visual picture of the family. Don't be too shocked. These are all projections based on fossil finds and predictions.
Like the primate tree,the hominin tree has many branches, not a direct line of descent to be studied neatly.
Ardipithecus ramidus is the latest link, a hominin that lived in trees but started to use bipedal features to succeed, despite living in a forest habitat. The favoured theory that bipedalism developed in a savannah habitat has to be adjusted now. We used to have six nice tidy reasons for people becoming bipedal when they started to live in a dry savannah. Can you recall what they are? They are at the bottom of the Biological evolution section if you can't remember them now.
Unfortunately now we have to start again with our selection pressures, as the evidence suggests that ancestors were fully bipedal before they left the forest. New selection pressures have to be discussed that could give an advantage to being bipedal in a forest habitat. What would make Ardipithecus families become bipedal? What advantage would it give them? Remember survival is all about getting the best mates, food or space to live,so the argument could go that males who carried more food back to the family with their free hands were better providers, so they were more likely to get to stay around the family.
This link goes to a lovely story about the ancestor known as Toumae, whose fossils were discovered in 2002. http://videos.howstuffworks.com/discovery-health/4911-100-greatest-discoveries-evolution-video.htm
Once you have learned the language of the evolution of the skull and face have a go at this interactive, identify the mystery fossil,
http://humanorigins.si.edu/evidence/human-fossils/mystery-skull-interactive
Practical task comparing the skull and cranium of hominins.
Use the skull set to measure the significant differences in the skulls we have available in class (Homo sapiens, Homo erectus, Australopithecus africanus and Gorilla). Compare the size of the forehead, brow ridges, chin, sagittal crest, zygomatic arch, mandible, angle or prognathism, the dental arcade, the position of the foramen magnum in each species.
What can you say about the trends for each feature?
Relate the biological change to a particular selection pressure that initiated the change.
http://www.sexyarchaeology.org/ website about discovery of human fossils
Human hand evolution
link to quick animation
showing hominin hands evolving. Remember that the modern apes have also continued to evolve their hands ,and our hand is more similar to the primitive hand than they are.
The modern human hand has a longer thumb than either the chimpanzee or gorilla, relative to the overall size of the hand. This allows human hands to make the precision grip that is associated with tool use. making our opposable thumb into a precise grasp requires a longer thumb, versatile muscles and co-ordination between the hand and eyes. The area of the brain dedicated to using the hand is really large (now - probably wasn't back in the day).
This website has a good set of photos and models to allow you to compare the different thumb/finger lengths in closely related primates.
http://www.handresearch.com/diagnostics/palmar-creases-hand-lines-primatology.htm
It is interesting to remember that the modern human hand has more similarities to Ardipithecus style hands than it does to Gorilla or Chimpanzee as their hands have become specialised for purposes other than grasping or tool use. The chimpanzee knuckle walking style is more advanced ( which means it has changed more ) than the human or the ardipithecus hand.
What was it about human evolution that changed the selection pressures acting on our hand, what were the reasons the hand did evolve?
Hard to imagine that just being bipedal meant our hand changed - what has that go to do with walking?
Its got everything to do with NOT walking quadrupedally. Hominin hands were NOW able to be used for other lifestyle advantages. They became adapted for other things, hands could carry food so your food supply was more successful, hands could carry the children (because we were less hairy in the open savannah the dependent young couldn't cling on so well anymore) and hands could be used to start tool cultures.
Natural selection is about the selection FOR an advantage (better at competing for food, for mates or for space to live and so the offspring represent more in the next generation) so these changes to the hand are a response to these advantages being able to sue your hands more gave hominins.
This podcast describes how our anatomy allowed our hands to be more useful.
http://www.npr.org/templates/story/story.php?storyId=128676181
The ongoing changes after these adaptations, and the subsequent changes in the brain , compounding with better dexterity as we used tools more and then the brain grows more and then the food is better so the brain grows more, is this never ending cycle of biology and culture interacting. (Not withstanding there has had to be some random mutation that worked out better - mutations are not a designed to order effect even if we make it sound like they are. There will have been many designs that didn't give an advantage so we don't know about them.)
Randomly Bipedalism means we have problems with our feet now!! Putting all the weight on our feet is not all good.
These guys have thought about it
http://ngm.nationalgeographic.com/print/2006/07/bipedal-body/ackerman-text and how some of the health issues people have are caused by poor design. Probably doesn't affect our evolution because most of the problems arise after people have reproduced, the problems don't affect our reproductive success.
http://www.pbs.or
g/wgbh/evolution/library/07/index.html has a great collection of video clips on significant fossil evidence in the human evolution story.
http://www.amnh.org/education/resources/rfl/web/meettherelatives/2.php a website to visit to compare skeletal organisation of Chimpanzee, Homo sapiens and Homo neanderthalensis
http://talkorigins.org/faqs/homs/species.html summary pages for hominin ancestors
Reasons to become Bipedal in the savannah
1 Eyes were lifted up to see across a bigger distance of grassland
2 and 3 Hands were free to Carry food and weapons
4 less body area exposed to heat of sun (just the head and shoulders)
5 walking upright was more efficient over longer distances (not faster over short distances)
6 cant remember, must be another one?
Link to efossils Summary of Bipedal ism
These pages are a summary of Changes to the Skeleton to do with being Bipedal, should be all familiar stuff.
Changes in the Skull
These are caused by different selection pressures - changes in diet and changes in intelligence both affect the skull. The dietary changes is related to tool use, the trend to increasing intelligence is related to diet and to communication and problem solving, and both affect the size of the brain related to the hand.
Great Interactives for this topic at
https://unlockinglifescode.org/interactive-overview
Cultural Evolution
Tools, Fire and Forward Thinking.
http://humanorigins.si.edu/evidence/human-family-tree
The Human Family tree is very bushy, all hominins are bipedal, what happens after that is due to cultural differences.
The Human origins website has a lot of information.
Being able to control language and symbols is a characteristic of Human evolution.
http://humanorigins.si.edu/human-characteristics/language
Tool cultures -to be finished -
Homo ergaster/erectus/heidelbergensis Becoming a Scavenger-competing by using Acheulian Tools - re-enacted in a video 10 minutes,
https://www.youtube.com/watch?v=cEt24uA1AIs
Hunt or Be hunted, bit of a misnomer because we weren't hunters, our ancestors were scavengers. Using the bone marrow to feed the growing brain, mastering Fire.
Watch the series,takes it up to neanderthal competing with homo sapiens.
https://www.youtube.com/watch?v=Y0qah4WZH-c
https://www.youtube.com/watch?v=JBASHHocjTc
https://www.youtube.com/watch?v=OWShsXF3OH0
Fire - tobefinished
Communication skills - to be finished
This link goes to a Cute video, not really at year 13 level, bit of an introductory perspective
Settlements and Domesticating plants and Animals
https://www.youtube.com/watch?v=-7bqi70B3tE This is a good series, but there are 15 episodes.
A brief expose` of the difference in the cultures in the last 10 000 years of our history,the paleolithic, mesolithic and neolithic tool cultures.
https://www.youtube.com/watch?v=-qq_1lcMrDM
This interactive In and Beyond Africa is a timeline that has information linked to the eras of human evolution, has a couple of cute games, not really year 13 level but makes a nice change from exam study eh.
Homo sapiens spread over the world.
There are several theories about how it came to pass that Homo sapiens is the only branch of hominins left on Earth.
Evidence shows that Homo erectus spread out of Africa to Europe and Asia.
Did Homo erectus populations across the world continue to interbreed back wards and forwards to the populations in Africa, therefore spreading the new genes around the world and all H erectus evolved into H sapiens,
OR did a successful new Homo sapiens evolve from a group in Africa, develop a successful culture and expand their population so quickly that their species did not interbreed with the previous populations, out competed the old style of living and became the only population as they migrated across the planet?
You must understand the evidence for both theories.
These are the two theories for our discussion. The Multi Regional Theory and the Replacement Theory. There is evidence for and against each theory being the correct explanation for how Homo sapiens was left as the only human species. Both theories agree that Homo erectus left Africa first.
Then they differ.
Think about what the two ideas are saying.
If the multi regional theory is supported some places will have older style fossils which will interbreed with new types and will create instantly across between the two, a half breed or transitional fossil, maybe a slopey face with a biggish forehead!! Maybe a early type fossil with tools that are more H sapiens style, these groups would make a genetic change that works for them, breed with neighbouring groups, sharing their genes around the world over a few generations. The genes they are sharing would be very diverse as they would have accumulated variations from across the world. A new cultural tool or mutation would have arisen in a variety of places, being shared widely so there would be no one specific place where oldest H sapiens tools come from. The variation in the genes would be very wide because the populations are very old.
The time span involved here is 1 million years. Generations of gene flow between many populations around the world caused the H erectus to evolve into H sapiens.
If the replacement theory is supported then the oldest sites of H sapiens fossil evidence will start off in Africa and spread out from there. The populations that left Africa probably would not interbreed back to the old groups in Africa, African populations in Africa would continue to change so their mutations would not be present in the populations that have descended from the ones that had left. The two bloodlines will be quite different. The younger descendants would have only their original DNA. like a population bottleneck, to work with. Scientists can't track the changes in nuclear DNA because of the cross over and recombination, but they can follow the mitochondrial DNA. This DNA is directly inherited from the mothers egg, only, so it is an exact copy of the mothers DNA. Any mutations between mother and child are entirely traceable. They show the family lineage as mutations accumulate. Populations that are separated will not have the same mutations that appear in the DNA.
The time span involved here is 140 000 years. This is a very recent separation. The mt DNA will not be very diverse as the population is a very small one.
What does this evidence look like?
Question 2013 NCEA
Analysis of genetic and fossil evidence (made over a number of years by a number of researchers) has indicated the following information about human dispersal:
1 Non-African males share a common ancestor about 140 000 years ago.
2 All humans share a common ancestor about 200 000 years ago.
3 Fossils (such as “Peking man” dated as about 750 000 years ago in Asia) seem to show a combination of H.sapiens and H.erectus type features.
4 Africans are more genetically diverse than other races.
5 Non-Africans include small (1-4%) traces of ancient hominin DNA (such as H neanderthalensis).
Use some or all of the above evidence to discuss the likely origin of modern humans.
In your answer:
Best answer.....
use the dates to match the theories,
use the diversity of the DNA to match the theories,
Use all the evidence to back one theory or the other. Neither of us have to decide which one is the right one, luckily, all we have to do is analyse the evidence both sides present.
So look further into the fine points.
http://www.bradshawfoundation.com/journey/ map showing timeline for Human dispersal according to one theory.
with a lot of information about the mt DNA and the Y chromosome evidence.
And a more simple version
https://unlockinglifescode.org/iaba/# gives key times and evidence.
In class students always say, well can't they both be right, a mix of them both, why does it have to be one or the other, and now there is a paper that says maybe it is both!!
https://unlockinglifescode.org/explore/our-genomic-journey/feature-story-our-tangled-family-ties But what matters for us is what will the exam be about? Can you tell the main ideas for both theories?
Variations in mt DNA are used for evidence for many human mysteries, for example the old chestnut The Russian Tsar and his family who were massacred in WWI, this interactive explains how similarities in mt DNA bases link family members.
http://www.geneticorigins.org/mito/mitoframeset.htm
It is hard to understand the significance of the mt DNA, browse all the links at this page,
http://humanorigins.si.edu/evidence/genetics
Study the neanderthal DNA sequences, the video, decide whether the evidence here supports the Multi-regional Theory or the Replacement Theory of Homo sapiens dispersal.
The slide show above gives evidence for each of the theories of dispersal. You might have to copy and paste the link.
And then the Neanderthal DNA found in Non Africans messes up the nice tidy theories. Remember that is why Science is always changing - as new evidence comes along, the scientists has to rethink. Can't deny the evidence. Has to alter the theory.
This clip is quite slow moving, you should know enough to understand it.
https://www.youtube.com/watch?v=No_Id8H4dv8
Following the differences in neanderthal mt DNA and mutations in modern mt DNA gives a timeline for the two groups to have a common ancestor.
http://www.geneticorigins.org/mito/mitoframeset.htm. You can guess your way through this interactive, but working it out is easy too.
Different angle on Dispersal.
Sometimes the question is not comparing the two theories. It is about why the population was successful and able to expand.
Why did humans leave Africa? (What were the selection pressures?) same as always - population pressure - the population got bigger where they were living) so they were under pressure to expand their range, and the environment changed ( the sea level dropped so the land bridges and islands were accessible). The population increased through better food supply, and some believe the impact of surviving grandmothers! They lived until their mid 30's now and could help their daughters raise their children, the mother had someone to give advice and get extra food for their grandchildren.
Movie that illustrates the trek Out of Africa (takes ten minutes)Revision activities
exam question support
http://www.studyit.org.nz/communicate/viewtopic.php?t=15664 , this is a good site for the latest help using other students questions and other teachers answers.
A summary timeline, you should be able to argue these points on the timeline.
http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive
http://www.quia.com/cm/60874.html for a quick quiz activity on Hominin ancestor facts
http://www.quia.com/jg/499827.html for a review activity going over some dates for Cultural events for Homo sapiens.
http://dsc.discovery.com/tv-shows/other-shows/videos/other-shows-discovering-ardi-videos.htm How do scientists work these things out?
Great slideshow that covers a lot of information.
http://www.slideshare.net/smullen57/3-human-evolutionhttp://www.slideshare.net/smullen57/3-human-evolution
See the Whole Course presented on a great New Zealand website, for everything you need to know all over again,some great links too. http://www.passbiology.co.nz/biology-level-3/human-evolution